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R. C. ARTER MACHINE SWITCHING TELEPHONE SYSTEM Filed June '7. 1920 3 Sheets-Sheet 1 I A. 67 %r/en @51 64).: abtozmeq 1 May 22, 1923;

R. C. ARTER MACHINE SWITCHING TELEPHONE SYSTEM Filed June 7. 1920 3 Sheets-Sheet 2 Swuewfoz 1 7 f1. 6'. 757/62. @513 45421 (ii/tonne WWA May 22, 1923.

R. C ARTER MACHINE SWITCHING TELEPHONE SYSTEM Filed June '7, 1920 3 Sheets-Sheet 5 Patented May 22, 1923.

UNITED STATES PATENT OFFICE.

ROY C. ARTER, OF GALION, OHIO, ASSIGNGR TO THE NORTH ELECTRIC MANUFAC- TURING COMPANY, OF GALION, OHIU, A GORPQRATION OF OHIO.

MACHINE-SWITCHING TELEPHONE SYSTEM.

Application filed June '7, 1920. Serial No. 387,275.

To all whom it may 0011 0cm Be it known that I, For C. AR'rnn, a citizen of the United States, residing. at Galion, in the county oit Crawford and State of Ohio, have invented a certain new and useful Improvement in Machine-Switching Telephone Systems, of which the following is a specification.

This invention relates to improvements in machine switching telephone systems, and particularly in the selecting and switching circuits of machine switches.

According to one ot the features of the invention, connections may be established between a line and an idle one oi a plurality of lines divided into groups, by first selecting the desired group and connecting with all the lines contained therein and then disconnecting all but one idle line which is retained for the purpose of establishing; a de sired connection. Due to this met 10d of selection, the so-called trunk hunting operation is obviated and a line may be instantaneously seized.

Other features of the invention have to do with party line ringing, improved test circuits, improvements in impulse control circuits and various other elements of machine switching systems, as will appear from the following description and the appended claims.

In the drawings, 1 illustrates the circuits of trunk finding and trunk selecting switches; Fig. 2. the circuits of connector switches. and Fig. 3, counting relays that co-operate in the control. of connector switches.

General description of the system.

The present system is a thousand line machine switching telephone exchange system, in. which connections are established under the control of calling parties. By means of a calling device of any well known design, such as that shown in the application of A. H. Adams, Serial No. 488,606, filed July 30, 1921, the calling party sends out impulses representing the hundreds, tens and units digits of the called line number and, finally, impulses for controlling the selection of ringing current of. the desired frequency to ring the bell of the station wanted on the called line.

The machine switches used in the establishment of a connection are inulti-contact switching relays, preferably of the type disclosed in latent No. 1,091,193 to E. E. Clement. Three sets of relay switches are used for the establishment of connections: one set, finder relays 110 and 120, to connect the calling line with an idle one of a plu-.

rality 0t selector trunks; a second set, selector relays 180 and 190, for connecting the selected trunk with an idle one of a plurality ct connector trunks, the hundreds designation of which corresponds to that of the called number; and. a third set, connector relays 280 and 290, for connecting the selected connector trunk with the called line. Be lays 110 and 120 are automatically operated upon the initiation. of a call, relay 190 is operated in accordance with the hundreds digit oi? the called number, relay 180 is automatically operated to connect an idle trunk of the group designated by relay 190, relay 290 is operated in accordance with the tens and relay 280 in accordance with the units digit of the called number.

The relays like 110 carry the answering and the relays like 290 carry the calling terminals of lines. All the answering terminals ot a line are multiplied together and with the inultipled calling terminals of the respective line. The calling and answering terminals comprise a set oi: three contacts through which the l ne and test conductors of a substation may be connected with a select-or trunk like ll and a connector trunk like 17'; -17 3. The number of the selector and connector trunks depends on the requirements oi"? the traliic. all the trunks being arranged lilte the ones disclosed in the drawings.

Associated with the answering end 01" each selector trunh like A there is a multL-contact relay like U5. The contacts of. this relay are divided into two groups (it ten contacts. The contacts in one group represent the units digits 1-4 and the contacts in the other group the tens digits 1-4). These contacts are connected, on one hand, with the front contacts of the various line relays like 101, and, on the other hand, with the windings of the various relays like 110 and 120 associated with the answering end of the respective trunk. The connection with the line relay contacts is in accordance with the tens and units numerical designation of the respective line, and the contacts of each line relay are multipled to the contacts of as many relays like 115 as there are trunks to which the line should have access upon the initiation of a call.

One switching relay like 110 is associated with the answering end of each selector trunk to connect it with a certain group of ten subscribers lines, each relay carrying 31 contacts, thirty of which are in ten sets of three, one set individual to each line. There are ten relays like 120 associated with the answering end of each selector trunk. The tens contacts of a relay 115 are con nected in numerical order to the windings of the various relays 11.0, and in a similar man ner the units contacts of a relay 115 are connected to the windings of the various relays 120 associated with the answering end 01 the respective selector trunk.

Upon the initiation of a call, it the trunk A is idle, the relay 115 is actuated, and depending on the identity of the calling line, a certain pair of line finder relays like 110 and 120 are operated to connect the line with the trunk. It the trunk A is busy, then the relay 10 1 is in actuated condition, and the initiation of the call results in the operation of a relay 11. associated with the next idle selector trunk. This relay causes then the extension of the calling line to the last mentioned trunk The relay 10%", associated with this trunk, may similarly extend the call to the succeeding selector trunk, etc. lVhile a selector trunk is being selected, a relay 103, associated therewith, is maintained energized to prevent the initiation of calls within the group of lines having access to the mentioned trunks. It should be noted in this connection that instead of the specific circuit arrangement herein disclosed, various arrangements. e. ,gn, like the one shown in Patent No. 1,252,97 41- to H. G. ehster, may be employed for controlling; the operation of switching; relays without departingfrom the spirit of the present invention.

Associated with each selector trunk, there is a set of counting relays 131-14-O. One pair of counting relays is provided for each of the digits 1-O. only three pairs of relays being illustrated in the drawings. The lefthand outer contacts of relays 131-14t0 lead to the first. second, etc, hundreds selector relays 190, 190, etc. These counting relays are operated by the calling party sending current impulses representing the hundreds digit of the called number. In accordance with the operation of the counting relays, a certain one of ten luinclreds-select int;- relays (190, 190% etc.) is actuated. The contacts of these selector relays are connected to connector trunks like 171-- ---173,

l.74l176. The relay 190 represents the hundreds digit 9, and the trunk conductors l71l73 are inultipled to the contacts of a plurality of relays representing this digit and associated with the various selector trunks. The connector trunks connected to the contacts of the relay 190 all serve for giving access to subscribers lines, the hundreds designation of which is 2. Depending" on the idle or busy condition of the con-' nector trunks terminating in the contacts of the actuated. relay 190, a certain one of the trunk selecting relays 18()18O is actuated. These trunk selecting relays are also associated. with the cal lingend oi": the selector trunk, the number of such trunk selecting relays associated with a trunk being determined by the number of connector trunks to which a selector relay has access. The trunk selecting relays operate to connect the calling end of the selector trunk with a selected connector trunk through any one of the hundreds-selector relays actuated under the control of the counting relays.

A set of counting relays 301-4310, is associated with each connector trunk. These counting relays are operated in accordance with the tens, units and stations lll'lPUlSGS. The bottom contacts of relays 301--310 are connected in multiple to the first, second. etc. tenth contacts of relays 275, 285 and 295. Under the joint control of the counting relays and relays 322 and 295, a tens connertor relay like 290 is actuated. This connector relay represents the tens digit of the called line, ten such relays representing the various tens digits being associated with the calling end of: each connector trunk. Each subscribers line is inultipled to the contacts of a plurality of tens connector relays represeuting the designation of the line. The relay 295 is provided in common to all the tens connector relays of a connector trunk.

Under the control of the counting relays, operated in accordance with the units iinpulses, and relays 324 and 285, :1 units con-- nector relay like 280 is operated, The calling end of each connector trunk is provided with ten units connector relays reprcsenting the various units digits, the contacts of these relays being multipled, on one hand, to the conductors. o'l the associated connector trunk. and. on the other hanrhto the contacts of the tens connector relays associated withthe trunk. The relay is provided in common to all the units connector relays of a trunk.

The counting relays are again operated, now in accordance with the designation of the party line station desired, and operate through the agency of relays 327 and 275, one of the relays 211214 to select the proper ringing; current tor signaling the desired station. 3

and front contact, the left-hand armatures and back contacts of relay 132-109, and the top contacts of relay 162 to ground at the armature of relay 104. The relay 151 connects grounded battery through the winding of relay 154, the left-hand back contact and armature of relay 153, the left-hand front contact and armature of 152, and the armature and back contact of relay 151 to ground at relay 104. The relay 154 looks up through its left-hand contact. Upon the the following closure of the line-circuit, the relays 106 and 107 again close their front contacts, but for an insuflicient length of time to permit relay 151 to attract its armature, which is retarded by mechanical means. The ground from the armature of relay 104 is extended through the front contact and armature of relay 107, the right-hand armatures and back contacts of the relays 109132, the righthand armature and front contact of the relay 131, and the winding of the relay 131 to grounded battery. The relay 131 becomes energized and locks up in the same manner as relay 108. In its right-hand back contact, the relay 131 opens the locking circuit of the relay 108 and the latter becomes deenergized.

Upon the second interruption of the line circuit, the relay 107 connects through its back contact, the left-hand inner armatures and back contacts of the relays 140--132, the left-hand inner armature and front contact of the relay 131, and the winding of the relay 1.32 to grounded battery. This relay becomes energized and locks up through the path traced for the relay 131. In its left-hand back contact, the relay 132 opens the circuit of the relay 131 and the latter becomes de-energized. The following closure of the line circuit results in the closure of a circuit for the relay 132 through the right-hand front contact and armature of the relay 132, the right-hand armatures and back contacts of the relays 133-109 in series, and the front contact of relay 107. The relay 132 becomes energized, locks up and opens the locking circuit of the relay 131.

This last closure of the line circuit is of relatively long duration, and for this reason the slow-to-pullup relay 151 is permitted to attract its armature. A circuit is now closed from grounded battery through the winding of relay 153, the right-hand front contact and armature of relay 154, the front contact and armature of the relay 151, and the top contacts of relay 162 to ground. The relay 153 is energized and locks up through its right-hand inner armature and front contact. Ground is now supplied through the right-hand outer armature of relay 153, the lefthand outer armature and front contact of relay 132, and the winding of relay 190 to grounded battery. The relay 190 becomes ground energized and locks up through its bottom contacts, a resistance 191, and the left-hand contact of relay 104 to ground.

Connector tmmlc selection.

low-up contact of relay 201, conductor 172,,

the sixth or test contacts of relay 190, the armature and front contact of the relay 162, and the Winding of relay 180 to grounded battery. The relay 180 becomes energized, but the current flowing through the low resistance left-hand winding of the relay 201 i is not sufficient to energize the latter. The relay 180 looks up through its bottom con tacts, the winding of relay 161 and the lefthand front contact of relay 104 to ground. The current flowing through this locking circuit causes the energization of relay 161, whereupon the circuit of relays 107 and 106 is interrupted in the right-hand armature and baclccontact and the circuit of relay 162 is opened in the lefthand back contact of relay 161. Upon the opening of the top front contact of the relay 162, the relays 152, 153, 154, 1.32 and 132' are unlocked, and these relays, together with relay 151, become (lo-energized. Furthermore, a circuit is closed fIOIIl' grounded battery through the outer armature and front cont-act of the relay 104, the left-hand armature and front contact of the relay 161, the fifth armature and back contact of the relay 162, the third contacts of relay 180, the back contact and armature of the relay 162, the test contacts of relay 190, conductor 172, the follow'up contacts and left-hand Winding of relay 201,.

and the left-hand armature and back contact of the relay 204 to ground. Direct battery being connected to its winding, the relay 201 beeomes energized and locks up from ground through its high resistance right hand winding, left-hand armature and front contact and the conductor 17 2. A relay like 180 cannot become energized in series with such high resistance winding.

Upon the de-energization of the relay 106, the circuit of the relay is opened, but before the latter has time to release its armature, a circuit is closed from grounded battery through the winding of relay 106. the contacts of relays .120 and and the calling line circuit, the top contacts of the relays 180 and 190, conductor 171, and the winding of relay 202 to ground, re-energizing relay 106, and maintaining relay 105 in its actuated condition. Relay 202 is energized.

In its right-hand inner front contact and armature, the relay 201 connects ground to the left-hand armature and bank contact of relay 204$ associated with a second connector trunk in the two hundreds group, and to the right-hand armature of relay 201 associated with this trunk. Therefore, upon the energizati on of another relay like 190, instead 01 trunk 17ll 73, trunk 174-4176 in the same group will be seized. The former cannot be seized on account of the high resistance path closed through the right-hand winding ol. the relay 201, and the latter i ay now be seized, because the test conductor 1T5 is supplied with ground. As soon as the trunk lie- 176 becomes busy and the relay 201" attracts its armaturos, the ground is extended to the next succeeding connector trunk in the same group, etc, until the last connector trunk is reached. When the trunk 171173 becomes idle, it may he again selected to the exclusion of all other trunks in its group. The test conductors of all the connector trunks are simultaneously connected through the contacts of relay 162 to relays 180, 180, 180", etc, respectively, and the relay 180 corresponding to the first idle connector trunk is actuated to extend the circuit A to this trunk. Immediate seizure of an idle trunlr is made therefore regardless of the number of trunks already in use, and immediately tlollow'ig the seizure or": this trunk, the remaining trunks are released and are available for other calls.

Upon the energization of relay 202, current paths are closed from grounded battery through the winding of relay 330, the upper hack contacts and armatures of relays 3013l0 in series, and in series through the Winding oi? relay 320, and then through the left-hand outer back Contact and armature of relay 203, the front contact and armature ot the relay 202, the left-hand hack contact and armature oi the relay 209, the right-- hand back contact and armature or the relay 204., and the right-hand outer front contact and armature ot the relay 201 to ground. The relay 380 attracts its armatures and, somewhat later, the relay 320 attracts its mechanically retarded armature. The relay 330 locks up through a circuit including its upper front contact and armature, the upper back, contacts and armatures of the relays 30l 3l0, the back contact and armature oi"? relay 340, the left-hand back contact and armature of relay 209, the right-hand back contact and armature of relay 204-, and the right-hanrfl outer front contact and armature of relay 201 to ground. The relay 320 closes a circuit from grounded battery through the winding of relay 321, the upper back contacts and armatures oi' relays 322, and 326 in series, the front contact and armature of relay 3-20, and then to ground at the armature of relay 201. The relay 321 looks up through its upper front contact and armature, the upper back contacts and arma tures of relays 323, 325 and 32" in series,

and then to ground at the armature of relay 201.

Tens selection.

The calling party causes now the sending or the tens impulses. In the present case, assuming the tens digit to be 3, he operates the dial to cause three short circuit interruptions. The relays 106 and 202 respond to these impulses. its in the case of the hundreds impulses, the relay 105 maintains its armature attracted, and the relay 320, like the relay 151, responds to the first inter ruptions of the circuit and releases its armature. The relay 320 does not attract its armature until the termination of this series oi impulses. In its back contact the relay 820 closes the energizing circuit of relay 322. A further result or the first deenergization oi? relay 202 is the closure of circut from ground through the contacts of relays 201, 204- and 209, the armature and back contact of relay 202, the middle arniatures and back contacts of relays 310--301 in series, the lower armature and trout contact of relay 330, and the Winding of relay 301 to grounded battery, The relay 301 becomes energized and locks up through its lower armature and front contact and the lower armatures and back contacts of the relays 302-840 in series, and then to ground at the relay 201.

Upon the following short closure of the line circuit, the relays 100 and 202 are again actuated, and the latter closes a circuit from ground through its armature and front con tact, the left-hand outer armature and back contact of the relay 203, the Winding of relay the upper armatures and back contacts of the relays 310-802 in series. the upper armature and front contact of relay 301, and the winding of the relay 301 to grounded battery. The relay 301 opens the circuit of relay 330 and locks up through the upper armatures and back contacts of relays 302-310, and the armature and back contact of relay 34:0 to ground at relay 201.

In a similar manner, the second circuit interrupt-ion results in the energization of relay 302, and. upon the following closure of the circuit the relay 302 is operated. The relay 302 opens the locking circuit of the relay 301, and the relay 302 that of relay 301. The third circuit interruptioncauses the operation oil relay 303, whereupon the relay 302 is unlocked.

The last relatively long circuit closure follows now. First, relay 803 is energized and causes in turn the de-energization of relay 30 A. short time thereafter, the relay 320 attracts its armature and establishes a circuit from ground at the armsture of relay 201, its armature and front contact, the inner armatures and back contacts oi: relays 326 and 824, the upper arma ture and front contact of relay 322 and the winding of relay 323 to grounded battery. The relay 323 locks up and opens the locking circuit of relay 321. A. circuit is now closed from ground through the contacts of relays 201, 204 and 209, the top armatures and back contacts of relays 327*324: in series, the top armature and front contact of .relay 323, and the winding of relay 295 to grounded battery. The desired tens connector relay is new energized over the following path: from groruided battery through the winding of #3 tens relay 290, the #3 contacts of relay 295, the lower armature and front contact of relay 303", the back contact and armature of relay 3&0, and then to ground at the armature of relay 201. The relay 290 looks up through its bottom contacts, a resistance 291, and the right-hand outer front contact and armature of the relay 201 to ground. At the same time, the ground applied to the third contacts of relay 295 by relay 303 is extended through the bottom contacts of the relay 290, the innermost contacts of relay 295, and the winding of marginal relay 340 to grounded battery. The relay 34L0 becomes energized and opens in its back contact the locking circuits of the relays 303 and 303. The relay 303 removes direct ground from relay 290. This does not release relay 290 which is held up through resistance 291, but causes the de-energization of the marginal relay 3 1 .0 which adjusted so that it will not hold up in series with resistance 291. The relay 303 recloses the originally traced energizing circuit of relay 330.

Units selection.

In accordance with the numerical designation of the units digit, which was assumed to be 1 the calling party produces now a single interruption in the line circuit. The relay 320 becomes de-energized upon the opening of its circuit in the front contact of relay 202, and closes a circuit from ground atthe armature of relay 201, through its armature and. back contact, the lower armature and back contact of relay 325, the lower armature and front contact of relay 323, and the winding of relay 32 1. This relay attracts its armatures, opens the energizing circuits of relays 322 and 295 and closes a locking circuit for itself through its lower front contact and armature and the lower back contact and armature of the relay 326. The relay 301 is again operated over its above traced path and locks up.

The closure of the line circuit at the calL ing station results in the energization and locking up of the relay 301 and the subsequent de-enerization of the relay 330. vShortly thereafter, the relay 320 pulls up its armature and connects ground through its front contact, the inner armature and back contact of the relay 326, the inner front contact and armature of relay 324, and the winding of relay 325 to grounded battery. Relay 325 becomes energized, unlocks relay and locks up through the inner back contact and armature of relay 327. A circuit is now closed from ground at the armature of relay 201 through the top arinatures and back contacts of relays 32'? and 326, the top armature and front contact of relay 325, and the winding of relay 285 to grounded battery. This relay becomes energized and closes a circuit from grounded battery through the winding of #1 units relay 280, the :ttl contacts of relay 285, the lower front contact and armature of relay 301, the back contact and armature of relay 3&0, and then to ground at the relay 201. The relay 280 becomes energized and closes a locking circuit for itself through its bottom contacts, resistance 281 and the armature and front contact of relay 20.1, and in parallel an energizing circuit for the marginal relay 340. The relay 3 10 opens the locking circuits of relay 301 and 301, whereupon the relay 34:0 becomes de-energized. The circuit of relay 330 is again established, and this re lay locks up.

Testing 0/ called Zine.

Upon the actuation of relay 280, a test circuit is closed from ground through the high resistance left-hand winding of a marginal test relay 215, the third (test) con tacts of relays 280 and 290, and the winding of the called line cut-ofl relay 292 to battery. The relay 215 does not become energized unless full battery potential is applied to the test contacts of the connector relays, and this is the case only if no other test relay is included in a series circuit with the called line cut-off relay. Assuming that the called line is idle, the relays 292 and 215 become energized. The relay 292, by attracting its armatures and thereby disconnecting line relay 293, prevents the initiation of calls by the called party, and the relay 215 closes a locking circuit for itself through its low resistance right-hand winding and the above traced test circuit. The test potential on the multiple test contacts of this called line is now reduced so as to prevent the energization of another test relay upon an attempted seizure of this line. in its left-hand outer armature and front contact, the relay 215 closes an encrgizing circuit for relay 208 and the latter attracts its armature.

Party Zine ringing.

Assuming now that the ringing of station a. is desired, the calling party dials 1,

causing a single circuit interruption. The relay 202 is momentarily tie-energized, whereupon the relay 320 releases its armature and the relay 301. becomes energized. Upon the de-energization of relay 320, a circuit is closed from grounded battery through the Winding of relay 320, the lower front contact and armature of relay 325, and the back contact and armature of relay 320 to ground. The relay opens the locking circuit of relay 324, and locks up through its lower front contact and armature. Upon the subsequent energization of relay 202, the relay 301 pulls up, opens the circuit of relay 830, and locks up to ground at the relay 201. The relay 320 attracts now its armature and closes an energizing circuit for relay 327 through the upper front contact and armature of the relay 326. The relay 32? opens the circuit of relay 325, and locks up through its middle armature and front contact.

Through its top front contact and armature, the relay 32? connects ground to the Winding of relay 275, and the latter becomes energized. A circuit is completed from grounded battery through the winding of relay 211, the #1 contacts of relay 275, the lower front contact and armature of relay 801, the back contact and armature o1 relay 3410, and then to ground at the relay 201. The relay 211 becomes energized and locks up through its left-hand front contact and armature. In its right-hand inner front contact and armature, the relay 211 closes an energizing circuit for relay 209 and the latter, by opening its left-hand back contact, removes the ground from the locking circuits of relays 326, 327, 320, 301 and 301. The relay 209 being energized, the relay 330 cannot be re-energized. In its left-hand armature and front contact, the relay 209 extends the ground from the relay 201, through the winding of relay 206, the left-hand inner armature and front contact of relay 2'l5, and an interrupter 282 to grounded battery. Under the control of the interrupter, the relay 206 is intermittently ener ized and de-energized. While the armatures of relay 206 are in their oil-normal position, a circuit is closed from the 10 cycle ringing current generator through the right-hand outer armature and front contact of relay 2 t1, the right hand outer armature and back contact of relay 207, the lower front contact and armature of relay 206, the middle armature and front contact of relay 208, the second contacts of relays 280 and 290, and the ringers at stations 200 d and a. in parallel to ground. Only the ringer at station 200" is responsive to the 16 cycle current, and therefore only its bellwill be rung.

When the called party removes his receiver from the switch-hook and closes a bridge across the called line through the contacts of ninth contacts of the relay 275.

the switchhook and dial or calling device which are represented diagrammatically on the drawing, then, upon the next silent period of interrupter 282, the relay 206 extends this bridge over its back contacts and through the retardation coil 205 and the relay 204 to ground and battery. The relay 20 1- becomes energized and opens in its right hand back contact the circuit of relay 211. In its left-l1and front contact, the relay 20st closes an energizing circuit :lor relay 203, and this relay opens its left-hand back contact so as to prevent the re-energization of relays 320 and 330 during the restoration oi the connection. Upon the de-enersization of relay 211, the relay 209 becomes tie-energized, preventing the further operation of relay 206. The talking connection is now completed and the calling and called parties may converse with each other.

It should be noted that the left-hand a1 mature of the relay 207 is grounded, While the right-hand outer armature of this relay may be connected to the ringing generators of various frequencies-through the contacts of the relays 211-21 1. Depending on the normal or actuated condition of the relay 207, the relay 206 may thus connect ground or current source to either side of a selected line, making possible the selective ringing of stations, the bells of which are grounded from opposite sides of the line or bridged across the line. It the bells are bridged across the line, the selective ringing of only four stations is possible, the desired ringing current frequency being selected by causing the operation of one of the relays 211-214. If, however, the bells are grounded from opposite sides of the line. eight stations may be arranged on a line, and then their selective ringing is controlled by the mentioned relays 21121& and the relay 207. In this case, depending on the actuated or normal condition of the relay 207, the selected ringing current generator is connected to the tip or ring side of the line, all stations connected to the same side of the line being provided with dii'lerently tuned ringers.

The operation of the relay 207 is controlled by the calling party through the agency of relay 350. The winding of the relay 350 is connected to the lower armatures of the counting relays 306-810, and

the winding of relay 211 is multipled tothe first and sixth contacts of the relay 2T5. diniilarly. the winding of the relay 212 is inultipled to the second and seventh contacts of the relay 2i5, etc, and the winding oi relay 21% is multipled to the fourth and For this reason, whether the subscriber sends out one impulse or six impulses, the relay 211 will be energized under the control f counting relay 301 or 306. In the latter case, however,the relay 211 is included in a series circuit with the relay 350, and this relay closes a circuit "from ground through its armature and front contact and the winding of the relay 207 to grounded battery. The relay 207 is energized, locks up, and performs its above mentioned function. a

The relay 850 cannot be operated during the sending of the tens or units impulses. This is prevented by the closure of a shunt around the winding of relay 350, t the lower back contact and armature of relay 327, the left-hand back contact and armature ofrelay 209, the right-hand back contact and armature of relay 204:, and the outer iront contact and armature of relay 201 to ground. This shunt path is not opened until subsequent to the actuation of the relay 327, which occurs after the sending of the party line station designating impulses.

Disconnection.

When disconnection is desirec, the calling and called parties restore their receivers,

opening the loops closed across their lines. The relays 106 and 202 become de-energized upon the restoration of the receiver at the calling station, and the relay 20 1 upon the hanging up of the receiver at the called station.

The relay 106 permits the de-ei'iergization oi relay 105, and the latter opens the circuit of relays 104 and 102. The relay 10 i; removes the ground from the windings oil relays 110, 120, 161, 180 and 190. in the right-hand outer tront contact of relay 10a, the battery is disconnected from the wind ing of relay 201, but in order to prevent the seizure oi the connector trunk prior to the restoiation ot' the apparatus associated therewith, the relay 201 is maintained energized by a circuit extending from ground through its high resistance right-hand windlng, left-hand armature and front contact, and the left-hand inner front contact and armature otrelay 203 to grounded battery.

Upon the de-energization of the relay 20%, the circuit of relay 203 is opened. lay 203 causes the de-energization of the relay 201, whereupon the relays 280 and 290 are unlocked'and cause the restoration of relays 292 and 215. The relay 215 opens the circuit of relay 208.

If the called party restores his receiver first, then the holding" oi? the relay 2(1 is insured in the following manner: Upon the hanging up of the receiver at the called station, the relay 20 1 is tie-energized. It at this time the relay 202 is still operated, then a circuit is closed from grounded battery, through the winding, left-hand outer front contact and armature of relay 203, the front contact and armature oi the relay 202,

The re maintained energized and holds up relay- 201 tlnrough its middle armature and trout contact. This condition prevails until the relay 202 becomes (ls-energized, whereupon the connection is severed in the above de scribed manner.

Attempted seis we 0/ a busy Zinc.

As above stated, it the called line is busy, the relay 215 cannot attract its armatures. For this reason, the relay 208 remains in its normal condition and. the talking conductors are not connected with the selected called line. When the relay 209 is operated in response to the actuation of one of the relays 211-21 1, a circuit is closed from ground through an. interrupter 210, a condenser, the upper back contacts and arnlat-ures o't relays 206 and 200, conductor 171, the top contacts of relays 190, 180, 120 and 110, and the receiver at the calling station. The calling subscriber will perceive a tone in his receiver ii'idicating that the desired line is busy.

it may be desired to arrange the busy tone device so that it Will start up automatically when required instead of running contin-- uously. This is accomplished by adding a contact to relays 208 and 209. Upon the energization of relay 209, i'l the ringing relay 208 remains (lo-energized by reason of the fa ct that the wanted line is busy, a circuit is closed from ground at the outer right-hand armature of relay 201, the righthand armature and back contact of relay 204, the middle armature and front contact of relay 200 and the lower armature and back contact of relay 208. The ground placed upon the Start wire 220 may be utilized in the usual manner to initiate the operation of the busy tone device.

The calling party may now either hold the connection until the called line becomes idle or cause its complete restoration. In the former case, as soon as the called line hecomes idle, the relay 215 attracts its armatures, and by operating relay 208, removes the tone from the calling line. In its lefthand inner front contact, the relay 215 completes the circuit of relay 2 06, and the called station is signaled in the same manner as discussed in the previous case.

It the calling party elects to restore the connection, then by hanging up the receiver, he will cause the restoration oi relays 106 and 202. The relay 106 operates in the above described manner, and restores to normal all the apparatus shown in 1. The relay 203 being in its normal condition, upon the de-energization of the relay 104, the relay 201hecoines ole-energized and opens the circuits of all the relays that were loci-red up through its right-hand outeit' armature and front contact.

What is claimed is:

1. In a telephone exchange system, a line, a plurality of groups of other lines, each group bearing; a difierent numerical de gnaw tion, means for rendering busy said other lines, switching means associated with said line and operable in accordance with the numerical designations of said groups, other switching means associated with said line and operable in accordance with the busy or idle condition oi: said other lines, means for actuating said first mentioned switching means to select a desired group of lines, and means including said other switching means, operative thereupon for connecting said line directly to an idle one of said other lines.

2. In a telephone exchange system, line, a plurality of groups of other lines, each group bearing; a different numerical designation, means for rendering busy said other lines, switchingmeans associated with said line and operable in accordance with the numerical designations of qroups, other switching means associated with said line and operable in accordance with the busy or idle condition of said other lines, testing means associated with said other lines, means for actuating said first mentioned switchingn'ieans to select a desired group of lines and to close the circuits of the testing means of the lines of the latter group, and means including said other switching means opera tire thereupon for connecting said line directly to an idle onevof the lines of said group. I

3. In a telephone exchange system, a line, a plurality oi? groups of other lines, switch ing: means associated with said line and pro vided with contacts appertaining to said other lines, means for rendering said other lines busy, testing means associated with each of said other lines, means'lor actuating; said switching means to select a desired group of lines and close the circuits of the testing means of the lines of said group and means operative thereupon for actuating said switchino means to connect the line to an idle line or said desired group.

at. In a telephone exchange system, a plurality of lines, a plurality of groups of other lines, means tor rendering busy said other lines, two groups of switching relays, means operable in accordance with numerical iinpulses representing said groups of other lines for actuating a certain switching re lay in one of said groups, a plurality of contacts for each of the relays of said one of said groups in which lines or" a group terminate, and means controlled by the condi- -tion of said other lines for actuating a switching relay of the other group.

'5. ln a telephone exchange system, a plurality of lines, a pli'irality of groups oi other lines, means "for rendering busy said lines, two groups of switching relays associated with said plurality of lines, means operable in accordance with numerical impulses for actuating a certain switching relay in one of said groups, a plurality of contacts for each of the relays of said one of said groups in which lines of a group terminate, and means controlled by the condition of the lines terminating in the contacts of said certain switching relay for actuating a switching relay of the other group.

6. In a telephone exchange system, a plurality of lines, a plurality oi groups of other lines, means for rendering busy said other lines, two groups oi. switching relays associated with each one of said plurality of lines, a set of counting relays, means for actuating said. counting relays in accordance with numerical digits representing the different groups of other lines, means operable in accordance with the actuation of the counting relays for actuating a certain switching relay in one of said groups, a plurality of contacts for each of the relays of said one of said groups in which lines of a group terminate, and means controlled by the condition of the lines terminating in the contacts of an actuated switching relay of said one of said groups for actuating a switching relay of the other group.

7. In a telephone exchange system, a plurality of subscribers lines, a plurality of selector trunks, a plurality of groups of connector trunks, means for rendering busy said trunks, switching relays representin tens and switching; relays representing units digits of lines, means responsive to the initiation of a call for actuating a relay representing the tons and a relay representing the units designation of the calling line to connect the calling line with an idle seclector trunk, two groups of switching relays and a set of counting relays associated with each selector trunk, means controlled by the calling party for actuating said counting relays in accordance with a numerical digit oi the called line number, means operable in accordance with the actuation oi the counting relays for actuating; a certain switching relay inv one of said groups. a plurality oi contacts tor each of the relays of said one of said groups in which connectar trunks terminate, means controlled by the condition of the connector trunks for actuating; a switching; relay oi the other group to connect the selector, selector trunk with an idle connector trunk appearing in the contacts of the operated relay of said one of said groups, a set of counting relays and switching relays associated with each connector trunk representing the tens and units digits of subscribers lines, means controlled by. the calling party for operating the last mentioned set of counting relays in accordance with. the tens and units digits of the called number, and means operative thereupon for actuating a certain units and .a certain tens relay associated with the connector trunk. I

8. In a telephone exchange system, a plurality of subscribers lines, a plurality of selector trunks, a plurality of groups of con selector trunk, means controlledby the calling party for actuating said counting relays in accordance with a numerical digit of the called line number, means operable in ac .cordance with the actuation of the counting relays for actuating a certain switching relay in one of said groups, a plurality of contacts for each of the relays of saidone of said groups in which connector trunks terminate, means controlled by the condition of the connector trunksfor actuating a switching' relayof the other group to connect the selected selector trunk with an idle connec-tor trunk appearing in the contacts of the operated relay of said one of said groups, a set of counting relays and switching relays associated with each connector trunk representing the tens and units digitsof subscribers lines, means controlled by the callparty for operating the last mentioned set of counting relays in accordance with the tens and units digits of the called number, means operative thereupon for actuating a certain. units and a certain tens relay associated with the connector trunk, selec tive signaling means associated with each connector trunk, and means also. operable under the control of the last mentioned counting relays for variably operating said selective signaling means.

9. In a telephone exchange system, a line, a pluralityo't variously designated groups of other lines, two switching means, means for actuating one of said switching means in accordance with the designations oi said groups of other lines, test circuits for the lines of a group, contacts associated with one of the lines of a group for controlling the test-circuit ofanother line of the same group, and actuating circuits for the other switching means including said test circuits. 10. Ina telephone exchange system, allne,

plurality of variously designated groups o.t. ,l1nes, two groups of 1relaysassociated withsaid line, means for operating therelays of one group in accordance with the designation of the groups of lines, a test circuit for each one of said other lines, contacts associated with said other l1nes1ncluded in the test circuits of lines belonging to the same group, and actuating circuits for the relays ofthe other group including said test circuits and contacts of the relays of the said one of said groups.

11. In a. telephone exchange system,fa line,

a plurality of groups of other lines, means for rendering said other lines busy, test circuits associated with each of said other lines, switching means associated with the first mentioned line and responsive tothe? busy or idle condition of the other lines, and means for closing simultaneouslyall of the test circuits of the lines of 'one of said groups and the actuating circuits of said switching means. I I 7 12. In a telephone exchange system aline, a group of other lines, means for rendering said other lines busy, test circuits, a testamlay individual'to said first line and provided with contacts in said testcircuits,-a plu-P rality ofother relays provided with contacts appertaining to said first line, and means for actuating said test relay to close said test circuits and the actuating circuit of a certain one of said other relays, whereby the first"- mentioned line is connected to an idle one of the lines of said group.

13. In a telephone exchange system, a line, plurality of groups of other lines,- means for rendering said other lines busy,,test circuits associated with each of said other lines, a test relay individual to said first line and provided with contacts in said test circuits, a plurality of relays provided with contacts appertaining to said first .line, a plurality of relays provided with contacts in which the lines and test circuits. of said groups terminate, means for actuating one of the latter relays toselect a certain one of said groups,

and means for actuating the test relayttoof said groupterminate and. also provided with contacts insaidlcircuits, meansfor actuating the latter: relay, :and: means including saiditesting means and actuating circuits for thereupon. actuating. one of saidfplirrality of relays to connectsa-id firstmentioned line to an idle one of said other lines,

15. In a telephone exchange system, a line, a plurality of groups of other lines, means for rendering said other lines busy, testing means associated With said other lines, a plurality of relays provided with contacts in which the said groups of lines terminate and other contacts which are in the circuits of said testing means, a relay individual to said first mentioned line provided with contacts in the circuits of said testing means, means for actuating one of said plurality of relays to select a desired group of lines, and means including said testing means and said relay for connecting said line to an idle one of the lines of said group.

In Witness whereof, I hereunto subscribe my name this 1st day of June, A. D. 1920.

ROY C. ARTER. 

